1. Field of the Invention
The present invention relates to an obstacle detection system for a vehicle capable of detecting objects such as a forward vehicle and obstacles based on detected data supplied from object sensors.
2. Description of the Related Art
An obstacle detection system for a vehicle using a radar device has been widely known. For example, Japanese patent laid open publication No. JP H11-38141 has disclosed such a related-art obstacle detection system for a vehicle.
Such an obstacle detection system using the radar device emits a transmission wave such as laser light and millimeter wave around a vehicle within a predetermined sweep angle with a predetermined sweep cycle (or a scanning cycle). The obstacle detection system receives the reflected transmission wave reflected by the obstacle, and recognizes the existence of the obstacle. In the obstacle recognizing process, the obstacle detection system calculates a distance between the vehicle and the target obstacle object such as a forward vehicle based on the time length counted from the time of emitting the transmission wave (as laser light) to the time of receiving the reflected transmission wave from the obstacle object. Such an obstacle detection system is used for various applications, for example, a system for detecting a forward vehicle as the obstacle object and activating an alarm so as to inform the existence of the obstacle object to the driver of the vehicle, and another system for automatically controlling the speed of the vehicle in order to keep a predetermined distance between the relevant vehicle and the vehicle.
In the related-art obstacle detection system disclosed in JP H11-38141, the scanning of the transmission wave as the laser light is performed while gradually changing the irradiation angle of the laser light, and one value “r” as the distance to an obstacle is determined based on a time length, per irradiation angle, from the irradiation to the reception of the reflected laser light from the obstacle.
However, because such a laser system inherently involves various matters causing errors, there is a possibility of being a difference between the calculated distance “r” to the obstacle and the actual distance to the obstacle. In other words, the calculated distance “r” includes an error.
The system disclosed in JP H11-38141 recognizes the obstacle as a point per transmission wave, and integrates continuous points in order to determine a range of the obstacle. In general, although each detected point has an error, the related-art system disclosed in JP H11-38141 causes an error detection and recognition in which different obstacle objects such as a vehicle and a pedestrian are recognized as one obstacle object (also referred to as “association error”) or one obstacle object is recognized as two obstacle objects (also referred to as “separation error”).
There are various types of object sensors such as a sensor equipped with a stereo camera other than a radar system. However, because each object sensor inherently involves obligatory detection error, the system using such an object sensor causes error recognition such as the separation and association of obstacles.